In recent years in consequence of the development and feasibilization of superconductive magnets, the desirability of decreasing their weight, increasing their current density, and conferring high stability thereon has come to find growing recognition. In the light of these factors, high purity Al, as compared with high purity Cu, proves to be a highly effective stabilizing material because it has specific gravity less than one third the specific gravity of Cu, manifests high electric conductivity at extremely low temperatures, possesses high thermal conductivity, exhibits a saturated property in terms of the effect of magnetic resistance, and so on.
The Al-stabilized superconductor heretofore known to the art has high purity Al wires stranded (and further fused, optionally, as with solder) around the periphery of a superconductive wire 2 such as of Cu/Nb-Ti or Cu/Nb.sub.3 Sn, for example, as illustrated in FIG. 1 (cf. Japanese Patent Application (OPI) No. 163383/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application")). The superconductor of this construction, however, is mechanically and electromagnetically inferior because the adhesion is not sufficiently strong between the Al wires 1 and the superconductive (Cu/Nb-Ti or Cu/Nb.sub.3 Sn) wire 2. When the entire composite is filled up with solder for the purpose of eliminating such drawbacks, the pretreatment of the Al wires generally turns out to be difficult because the surface of Al wires is covered with a stable oxide coating.